CN102466821A - Method for evaluating static correction by using seismic section of local exploding reflection surface - Google Patents

Abstract

The invention discloses a method for evaluating static correction by using a seismic section of a local exploding reflection surface in geophysical prospecting, comprising steps of: performing Fourier transform to time coordinates of a common midpoint gather to obtain the common central point gather of a frequency domain; establishing an underground exploding point pulse response array corresponding to each common midpoint for each frequency; synthesizing record of the underground local exploding reflection surface by the response array; performing the Fourier transform to the section to obtain the seismic section of the local exploding reflection surface of a time domain; and evaluating effect of the static correction by comparison between static data before and after the static correction and between the seismic sections of the local exploding reflection surface before and after the static correction. According to the method for evaluating the static correction by using the seismic section of the local exploding reflection surface, first-arrival pickup time and velocity stacking time are reduced, efficiency for evaluating the static correction is increased, meanwhile, influence of the velocity stacking on the evaluating of the static correction is reduced, and the accuracy in the evaluating of the static correction is improved.

Description

A kind of method of utilizing confined explosion's reflecting surface seismic section to estimate static correction

Technical field

The present invention relates to geophysical exploration technology, is a kind of technology of utilizing the ground observation data to synthesize other a kind of seismic data, can be used for utilizing confined explosion's reflecting surface seismic section to estimate the method for static correction.

Background technology

Static correction is a great problem of seismic prospecting, especially in the near surface structure areas with complicated.The static correction problem solves bad, just be difficult to imaging, if the static correction solution is fine, not only can forms images, and can improve the signal to noise ratio (S/N ratio) and the resolution of stacked section.But getting well and going bad of how to evaluate static correction just become another difficult problem, and the method for estimating static correction at present has three kinds of methods: the quality of the quality of first arrival, road collection data, stacked section.

The quality of judging static correction value with first arrival is very directly perceived, can observe face of land consensus information simultaneously, but some first arrival information and not obvious also possibly appear at the part that obviously improves above the first arrival, the situation that on stacked section, but can not form images.

The quality of judging static correction with road collection data is also very directly perceived, and on the higher road collection of signal to noise ratio (S/N ratio), the conclusion that obtains is reliable, but at the lower road collection of signal to noise ratio (S/N ratio), is difficult to differentiate the lineups of useful signal, can't make preferably and judging.

Judge that with stacked section the conclusion that the quality of static correction value obtains is reliable; Because the effect ultimate demand of static correction embodies on stacked section, but obtaining stacked section must pass through velocity analysis, and velocity analysis meeting labor intensive and computer resource; And inevitably receive man's activity; It is too big to estimate the required cost of paying of static correction quality like this, and the quality of the correctness of speed and static correction value mixes, and is difficult to resolution.

Summary of the invention

The object of the invention provides a kind of confined explosion's reflecting surface seismic section that utilizes of estimating the static correction effect apace and estimates the method for static correction.

The present invention realizes through following technical scheme:

1) gathers seismic exploration data;

2) geological data is reset, made up CMP gather;

3) time coordinate to CMP gather carries out the CMP gather D (x that Fourier transform obtains frequency field _m, h, ω);

In the formula, ω is a frequency, x _mBe the lateral coordinates of central point on ground, h is the geophone offset of CMP gather;

4) to CMP gather structure each the common midpoint place corresponding underground explosion point impulse response matrix G of each frequencies omega by frequency field _m:

G _m＝(A _m，N，A _m，-N+1，...，A _m，0，...，A _m，N-1，A _m，N) (1)

A _i，j＝D(iΔx，jΔh，ω)/S ₁(ω) (2)

In the formula, ω is a frequency, S ₁(ω) be the seismic wavelet of frequency field, Δ h, j and N are the half the of geophone offset SI, geophone offset label and geophone offset number, and Δ x, i are respectively common midpoint interval and label; A _{I, j}Be and underground explosion reflection spot and the corresponding impulse response of face of land acceptance point; D is the CMP gather that step 3) obtains; M is the number of plies of underground medium.

When the seismic wavelet of the frequency field described in the step 4) is unknown, be changed to 1.

The matrix that the seismologic record that underground explosion point impulse response matrix described in the step 4) obtains on ground when being propagated by real medium one half speed by the pulse that excites at underground explosion point place is formed, underground explosion are selected the point on all subsurface interfaces that are meant millet cake accordingly.

5) each frequencies omega is made up the underground face impulse response matrix G of confined explosion by underground explosion point impulse response matrix:

$G=\left[\begin{array}{ccccc}{A}_{m-M,-N}& ...& A_{m-M,0}& ...& A_{m-M,N}\\ ...& ...& ...& ...& ...\\ A_{m,-N}& ...& A_{m,0}& ...& A_{m,N}\\ ...& ...& ...& ...& ...\\ A_{m+M,-N}& ...& A_{m+M,0}& ...& A_{m+M.N}\end{array}\right]---\left(3\right)$

In the formula: M is half that the blast of composition confined explosion reflecting surface is counted.

6) by the reflecting surface record P of face impulse response matrix generted address confined explosion of underground confined explosion _{M, j}:

$P_{m,j}=\underset{k=-N}{\overset{N}{\mathrm{\Σ}}}{A}_{j,k}{S}_2\left(\mathrm{\ω}\right)w_k---\left(4\right)$

In the formula: S ₂Used wavelet when (ω) being generted address confined explosion reflecting surface record, w _kBe the weight coefficient of the reflection spot that respectively explodes in confined explosion's reflecting surface, P _{M, j}J road for the confined explosion reflecting surface record of corresponding m common midpoint:

Used wavelet was got S when the described generted address of step 6) confined explosion reflecting surface write down ₂(ω)=S ₁(ω), S ₁(ω) be the described seismic wavelet of step 4).

The weight coefficient of reflection spot of respectively exploding in the described confined explosion of the step 6) reflecting surface is got w _k=1.

7) make up the reflecting surface seismic section Q of confined explosion in frequency field by confined explosion's reflecting surface record _i

Q _i＝P _m，0 (5)

In the formula: Q _iI road for confined explosion's reflecting surface seismic section;

Confined explosion's reflecting surface seismic section of the frequency field that 8) step 7) is obtained carries out inverse Fourier transform, obtains confined explosion's reflecting surface seismic section of time domain:

q _i＝FFT ^-1(Q _i) (6)

In the formula: FFT ^-1Be inverse Fourier transform;

9) with before the static correction with static correction after geological data, according to step 1)-8) obtain before the static correction with static correction after confined explosion's reflecting surface seismic section, contrast confined explosion reflecting surface seismic section is estimated the static correction effect.

The described evaluation static correction of step 9) effect is that the zone of interest lineups after static correction become continuously, and energy strengthens, effective for static correction; Otherwise, be the weak effect of static correction.

When the present invention synthesizes confined explosion's reflecting surface seismic section; Only need original road collection; Do not need first break time and stack velocity, reduced the time of picking up first break time and stack velocity, improved the efficient of estimating static correction; Also reduce simultaneously the influence that stack velocity is estimated static correction, improved the evaluation accuracy of static correction.Because the signal to noise ratio (S/N ratio) of confined explosion's reflection horizon seismic section will be higher than raw data, the effect of static correction also can well be estimated in the area that the collection signal to noise ratio (S/N ratio) is lower in original road.

Description of drawings

Fig. 1 is confined explosion's reflecting surface seismic section of not using static correction value;

Fig. 2 is the confined explosion's reflecting surface seismic section after the application field statics.

Embodiment

The present invention extracts all geological datas earlier, obtains common center trace collection, does fourier transform then; Make up the impulse response matrix and the underground face impulse response matrix G of confined explosion of underground explosion point in frequency field; Generted address confined explosion reflecting surface writes down and local exploding reflector seismic section then.On the confined explosion's reflecting surface seismic section before and after the static correction, can estimate the effect of static correction fast.

Embodiment of the present invention is following:

1) gathers seismic exploration data.

2) geological data is reset, made up CMP gather.

3) time coordinate to CMP gather carries out the CMP gather D (x that Fourier transform obtains frequency field _m, h, ω).

4) each frequencies omega is made up the corresponding underground explosion point impulse response matrix G in each common midpoint place according to formula (1) and (2) _m:

5) each frequencies omega is made up the underground face impulse response matrix G of confined explosion by underground explosion point impulse response matrix according to formula (3):

6) according to formula (4), by the reflecting surface record P of face impulse response matrix generted address confined explosion of underground confined explosion _{M, j}:

7) in frequency field according to formula (5), make up the reflecting surface seismic section Q of confined explosion by confined explosion reflecting surface record _i

Confined explosion's reflecting surface seismic section of the frequency field that 8) step 7) is obtained carries out inverse Fourier transform, just can obtain confined explosion's reflecting surface seismic section of time domain:

9) with before the static correction with static correction after geological data, according to step 1)-8) obtain before the static correction with static correction after confined explosion's reflecting surface seismic section, contrast confined explosion reflecting surface seismic section is estimated the static correction effect.

Below be instantiation of the present invention:

1) obtains prestack seismogram.

2) original earthquake data is handled confined explosion's reflecting surface seismic section of not used static correction value according to step (2)-step (9).

Fig. 1 is confined explosion's reflecting surface seismic section of not using static correction value

3) on original prestack seismogram, use the field statics amount

4) to the pre stack data after the application field statics amount, handle the confined explosion's reflecting surface seismic section after the field statics amount that is applied according to step (2)-step (9).

Fig. 2 is the confined explosion's reflecting surface seismic section after the application field statics

5) before using the field statics amount with after confined explosion's reflecting surface seismic section on assessment static correction effect.

In the contrast of Fig. 1 and 2, it is relatively poor to find out that Fig. 1 does not use in confined explosion's reflecting surface seismic section of static correction value the lineups continuity, energy a little less than; Fig. 2 uses in the confined explosion's reflecting surface seismic section after the field statics, and the lineups continuity obviously improves, and energy strengthens.Can find out that through above contrast to this survey line, confined explosion's reflecting surface seismic section (Fig. 2) quality after the application field statics improves, quality of this explanation field statics amount is also better.

Claims (1)

1. method of utilizing confined explosion reflecting surface seismic section to estimate static correction, characteristics are to realize through following steps:

1) gathers seismic exploration data;

2) geological data is reset, made up CMP gather;

3) time coordinate to CMP gather carries out the CMP gather D (x that Fourier transform obtains frequency field _m, h, ω);

In the formula, ω is a frequency, x _mBe the lateral coordinates of central point on ground, h is the geophone offset of CMP gather;

4) to CMP gather structure each the common midpoint place corresponding underground explosion point impulse response matrix G of each frequencies omega by frequency field _m:

G _m＝(A _m，-N，A _m，-N+1，...，A _m，0，...，A _m，N-1，A _m，N) (1)

A _i，j＝D(iΔx，jΔh，ω)/S ₁(ω) (2)

In the formula, ω is a frequency, S ₁(ω) be the seismic wavelet of frequency field, Δ h, j and N are the half the of geophone offset SI, geophone offset label and geophone offset number, and Δ x, i are respectively common midpoint interval and label; A _{I, j}Be and underground explosion reflection spot and the corresponding impulse response of face of land acceptance point; D is the CMP gather that step 3) obtains; M is the number of plies of underground medium.

When the seismic wavelet of the frequency field described in the step 4) is unknown, be changed to 1.

The matrix that the seismologic record that underground explosion point impulse response matrix described in the step 4) obtains on ground when being propagated by real medium one half speed by the pulse that excites at underground explosion point place is formed, underground explosion are selected the point on all subsurface interfaces that are meant millet cake accordingly.

5) each frequencies omega is made up the underground face impulse response matrix G of confined explosion by underground explosion point impulse response matrix:

$G=\left[\begin{array}{ccccc}{A}_{m-M,-N}& ...& A_{m-M,0}& ...& A_{m-M,N}\\ ...& ...& ...& ...& ...\\ A_{m,-N}& ...& A_{m,0}& ...& A_{m,N}\\ ...& ...& ...& ...& ...\\ A_{m+M,-N}& ...& A_{m+M,0}& ...& A_{m+M.N}\end{array}\right]---\left(3\right)$

In the formula: M is half that the blast of composition confined explosion reflecting surface is counted.

6) by the reflecting surface record P of face impulse response matrix generted address confined explosion of underground confined explosion _{M, j}:

$P_{m,j}=\underset{k=-N}{\overset{N}{\mathrm{\Σ}}}{A}_{j,k}{S}_2\left(\mathrm{\ω}\right)w_k---\left(4\right)$

In the formula: S ₂Used wavelet when (ω) being generted address confined explosion reflecting surface record, w _kBe the weight coefficient of the reflection spot that respectively explodes in confined explosion's reflecting surface, P _{M, j}J road for the confined explosion reflecting surface record of corresponding m common midpoint:

Used wavelet was got S when the described generted address of step 6) confined explosion reflecting surface write down ₂(ω)=S ₁(ω), S ₁(ω) be the described seismic wavelet of step 4).

The weight coefficient of reflection spot of respectively exploding in the described confined explosion of the step 6) reflecting surface is got w _k=1.

7) make up the reflecting surface seismic section Q of confined explosion in frequency field by confined explosion's reflecting surface record _i

Q _i＝P _m，0 (5)

In the formula: Q _iI road for confined explosion's reflecting surface seismic section;

Confined explosion's reflecting surface seismic section of the frequency field that 8) step 7) is obtained carries out inverse Fourier transform, obtains confined explosion's reflecting surface seismic section of time domain:

q _i＝FFT ^-1(Q _i) (6)

In the formula: FFT ^-1Be inverse Fourier transform;

9) with before the static correction with static correction after geological data, according to step 1)-8) obtain before the static correction with static correction after confined explosion's reflecting surface seismic section, contrast confined explosion reflecting surface seismic section is estimated the static correction effect.

The described evaluation static correction of step 9) effect is that the zone of interest lineups after static correction become continuously, and energy strengthens, effective for static correction; Otherwise, be the weak effect of static correction.

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